1. Field of the Invention
The present invention relates to an image reading apparatus to read both sides of a document by passing the document through the image forming apparatus a single time. More particularly, the invention relates to an image reading apparatus, an image storage apparatus and an image forming apparatus that reduces size, lowers cost, and improves efficiency of reading a document with different data formats by sharing a same circuit for processing both sides of a document.
2. Discussion of the Background
In recent years, an image reading apparatus in a copier machine, an image storage apparatus, facsimile machine, scanner machine, multi peripheral machine comprising function of scanner, facsimile, and printer, is capable of reading both sides of document by passing the document through the image reading device a single time.
Some image reading apparatuses read one side of document by turning over document after finishing reading reverse side of document. But these image reading apparatuses have low efficiency to read document, because reading a document sequentially takes more time. And having to turn the document over may result in increased errors and paper jams in the document reading apparatus. Further, a document turning over device is another component necessary in the image reading apparatus for such duplex reading.
JP 2002-77596A proposes an image reading apparatus capable of reading both sides of a document by once passing the document through the image reading device. The image reading apparatus comprises image sensors at each side of feeding path of document. But the image reading apparatus comprises a first circuit of image processor for front side of document and a second circuit of image processor for reverse side of document. That causes increasing size of apparatus and cost.
Then JP 2006-13924A proposes an image reading apparatus to process related unique features of each image reading device, for example shading correction etc, according to light source and/or relation to image sensor, with front side of image data and reverse said of image data by each proper former processing device, and process the other generally process, for example filter processing, expansion/reduction processing and converting color processing etc, by same after processing device.
But the image reading apparatus comprises proper former processing device for each side of document data, is not satisfied with downsizing and reducing cost. And the image reading apparatus processes generally process with front side of image data instantly after former processing, but the image reading apparatus can not process generally process with reverse side of image data instantly after former processing, because the image reading apparatus stores reverse side of image data to a storage device temporally and reads out the reverse side image data and then process generally process with reverse side of image data. So efficiency is not different from reading each side sequentially.
Other technology for improving efficiency, enables an image reading apparatus to store both side of image data after processing by former processing device and read out the both side image data and combine the both side image data by programmable logic alley, and transmit to after processing device for processing. But the image reading apparatus needs two structure of circuit for after processing, resulting in an increased cost.
Further, reducing volume of image data for improve efficiency is caused of deterioration of image.
And these technology ignore about difference of image format of front side of image data and reverse side of image data.